2016 RVHS H2 Biology Prelims Paper 2 Questions

River Valley High School Pg 1 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II RIVER VALLEY HIGH SCHOOL YEAR 6 PRELIMINARY EXAMINATION II CANDIDATE NAME CENTRE NUMBER S INDEX NUMBER H2 BIOLOGY 9648/02 Paper 2 Core Paper 15 Sep 2016 2 hours Additional Materials: Answer Paper READ THESE INSTRUCTIONS FIRST Write your index number and name on all the work you hand in. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Section A Answer all questions in the spaces provided on the question paper. Section B Answer any one question on the answer paper provided. Circle the question attempted on the cover page. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 / 10 2 / 10 3 / 9 4 / 10 5 / 10 6 / 11 7 / 10 8 / 10 Section B 9 or 10* / 20 Total / 100 _____________________________________________________________________ This Question Paper consists of 23 printed pages.

River Valley High School Pg 2 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II Section A (80 marks) Answer all the questions in this section. 1 Fig. 1.1 shows electronmicrographs of a zebrafish cell undergoing mitotic cell division. Fig. 1.1 (a) Explain the significance of mitosis to the development of zebrafish. [2] (b) (i) Identify stage A. [1] (ii) With reference to Fig. 1.1, describe two visible features that support the identification in 1(b)(i). [2]

River Valley High School Pg 3 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II (iii) Explain the significance of stage D to cell division. [2] (c) Explain why sister chromatids are genetically identical. [3] [Total: 10]

River Valley High School Pg 4 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II 2 Human Immunodeficiency Virus (HIV) is a retrovirus which infects immune cells expressing CD4 receptor on its cell surface membrane. (a) Explain the term retrovirus. [2] In 2012, the United States Food and Drug Administration (FDA) approved the OraQuick In -Home HIV Test, which is th e first test kit which can be b ought at pharmacies. The test kit relies on the presence of antibodies against gp120 in blood. Antibodies are produced by immune cells in response to exposure to forei gn particles. If an individual had been infected by HIV for at least a month, there is a low probability of a false-negative result, whereby the kit incorrectly reports a negative result. Fig 2.1 shows the changes in concentration of HIV RNA and antibodies against gp120 in the blood stream after HIV infection. Fig 2.1 Adapted from Hunt, 2016, Virology, Microbiology and Immunology On-line. http://www.microbiologybook.org/lecture/hiv3.htm

River Valley High School Pg 5 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II (b) With reference to Fig 2.1, (i) describe how the concentration of gp120 antibodies in blood changes in relation to the concentration of HIV RNA in the first 3 months after infection; [2] (ii) explain how HIV RNA concentration increases in the first month after infection; [1] (iii) explain why presence of gp120 antibodies is used as a basis for the detection of HIV infection. [2]

River Valley High School Pg 6 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II Enveloped viruses like HIV leave the host cell via budding, but T4 bacteriophages use a different mechanism for release. (c) Explain why release of HIV differs from the release of bacteriophages. [3] [Total: 10]

River Valley High School Pg 7 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II 3 Part I An in-vitro transcription system allows a DNA segment from yeast to be successfully transcribed under the control of a eukaryotic promoter. Transcription of this DNA segment occurs when purified components (RNA polymerase II and general transcription factors) are added. However, this in-vitro transcription system using purified components occurs at low efficiency, as compared to that using nuclear extract. This suggests that an important gene regulatory protein present in the nuclear extract is missing from the purified components. (a) (i) State a possible identity of the missing gene regulatory protein. [1] (ii) Describe how the gene regulatory protein identified in 3(a)(i) could result in higher efficiency of transcription. [1] To search for the DNA sequence to which this gene regulatory protein binds, five segments located upstream of the transcription start site (+1) is each deleted in various experimental set -ups. The TATA box is located 15 ba se-pairs upstream of the transcription start site. Each deleted template is incubated with a non -deleted template, which serves as a control. The four deletion sites are shown in Fig. 3.1. Fig. 3.1 The transcription activity of these deletions in the transcription system using nuclear extract is shown in Table 3.1. Table 3.1 Deletion end point -10 -35 -60 -85 Activity in deleted template / a.u. 0 10 24 23 Activity in non-deleted template / a.u. 23 24 24 23 X

River Valley High School Pg 8 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II (b) With reference to Fig. 3.1 and Table 3.1, (i) describe the extent of change in transcription activity caused by different deletions. [2] (ii) Suggest a reason for the transcription activity at -10 deletion end point. [2] (iii) Deduce the binding site of the gene regulatory protein. [1]

River Valley High School Pg 9 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II Part II In a separate experiment that studies the effect of starvation on yeast cells, it was observed that the cells upregulate the synthesis of GCN4 protein when deprived of purine. The α subunit of eukaryotic initiation factor 2 (eIF2) was found to be phosphorylated, and this leads to increased translation of mRNA encoding GCN4. (c) (i) State the level of gene regulation employed for GCN4. [1] (ii) Explain why this level of gene regulation may be advantageous to the survival of yeast cells. [1] [Total: 9]

River Valley High School Pg 10 of 23 Year 6 H2 Biology 9648 Paper 2 2016 Preliminary Examination II 4 In pigeon, pigment distribution is controlled by two genes. In the presence of the dominant allele for spread pigmentation, no pattern is observed. Fig 4.1 shows the appearance of pigeon with spread and patterned pigmentation. In a farm, pure-breeding pigeon with spread pigmentation and pure-breeding pigeon with barless pattern pigmentation were bred, all the pigeons in the F1 generation have spread pigmentation. Patterned pigmentation Spread pigmentation Fig. 4.1 When the F 1 pigeons were allowed to interbreed, the phenotype and number of offspring were recorded. Pigeon with spread pigmentation 86 Pigeon with barless pattern pigmentation 8 Pigeon with bar pattern pigmentation 23 Use the following symbols to represent the alleles: S – Spread s – no spread B – Bar pattern b – barless (a) Draw a gen